Moisture content of paper in a paper machine is typically controlled by a multivariable controller such as an MPC (Model Predictive Controller). On the basis of measurements, the multivariable controller outputs control actions i.e. manipulated variables which control a plurality of actuators which, in turn, regulate the process such that the moisture content of the paper is at a target level. Also other properties associated more generally with a sheet or web can be controlled in a corresponding manner. However, the operation of a machine having a process related to sheet production needs further development.